This proposal requests a total of $188,610 for the purchase and maintenance of a crystalline structure determination system consisting of one automated diffractometer and a computer facility for structure solution, refinement, and graphics displays of molecular structure. The research to be conducted by the user group of three investigators is diverse and includes synthesis and reactions of analogues of ferredoxins and the catalytic sites of nitrogenase and oxo-transfer molybdoenzymes, the total synthesis of palytoxin, thermal decomposition mechanisms and catalytic hydrogenation reactions of organoplatinum compounds, the structure of the polysaccharide emulsan, and enzyme-catalyzed synthesis of sugars. All projects require rapid and precise molecular structure information, which can be provided by the proposed system.